To maximize conductor and turn density, the wire used in electrical inductors, transformers and the like may advantageously have a flat, rectangular cross-section, such as may be formed by compacting a cable (e.g., Litz cable) composed of a number of insulated conductors that have been helically wound together. The helical configuration of the conductors causes each to assume all positions within the cross-section of the cable, thus minimizing eddy current losses and skin effects that would otherwise be produced. A novel cable of this sort, having a thin strip of insulating sheet material interposed between the layers of which it is comprised, as well as a novel method and apparatus by which such cable can readily be produced, are described and claimed in copending application for U.S. Letters Pat. Ser. No. 235,706, entitled "Method of Producing Flat Stranded Magnetic Conductor Cable and Cable Produced Thereby" filed in the name of Robert Frank Meserve on Feb. 18, 1981, which application is of common assignment herewith.
While cable so constructed and configured is highly advantageous and in widespread use, difficulties arise when attempts are made to manufacture the cable utilizing magnet wire which is finer than about 30 AWG (American Wire Gauge units are used through the present specification), such as would be desirable if the cable were to be employed for the efficient transfer of electrical energy of relatively high frequency (i.e., above about 1,000 cycles per second, or one KHz). The difficulties arise primarily because of the flexibility and resilency of the fine wires, which causes them to resist permanent deformation under the conditions of formation and compaction utilized in the cable manufacturing process. Thus, the relatively high tensile forces that are developed in drawing the conductors through the several stations of the converting machinery exert a straightening effect upon the individual strands, causing them all to seek centered positions and to thereby frustrate the forming and compacting operations. The fine wires also tend to break under the tension applied during forming, which of course reduces the efficiency of power transmission through the finished cable.
Accordingly, it is a primary object of the present invention to provide a novel and effective method by which a flat, rectangular cable can be produced from a multiplicity of relatively fine wire strands.
It is a more specific object of the invention to provide such a method by which the fine wires are integrated into a stiffened and mechanically strengthened assembly, enabling them to be formed into a physically stable configuration of high electrical continuity.
It is also an object of the invention to provide a novel cable so configured and comprised, which cable is capable of efficiently transmitting electrical energy of high frequency, and contains a minimum number of broken wires.